School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK.
Department of Molecular Microbiology, John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK.
Microb Genom. 2022 Apr;8(4). doi: 10.1099/mgen.0.000801.
Symbioses between bacteria and their insect hosts can range from loose associations through to obligate interdependence. While fundamental evolutionary insights have been gained from the in-depth study of obligate mutualisms, there is increasing interest in the evolutionary potential of flexible symbiotic associations between hosts and their gut microbiomes. Understanding relationships between microbes and hosts also offers the potential for exploitation for insect control. Here, we investigate the gut microbiome of a global agricultural pest, the Mediterranean fruit fly (). We used 16S rRNA profiling to compare the gut microbiomes of laboratory and wild strains raised on different diets and from flies collected from various natural plant hosts. The results showed that medfly guts harbour a simple microbiome that is primarily determined by the larval diet. However, regardless of the laboratory diet or natural plant host on which flies were raised, spp. dominated medfly microbiomes and were resistant to removal by antibiotic treatment. We sequenced the genome of the dominant putative spp. ('Medkleb') isolated from the gut of the Toliman wild-type strain. Genome-wide ANI analysis placed Medkleb within the group. Species level taxonomy for Medkleb was resolved using a mutli-locus phylogenetic approach - and molecular, sequence and phenotypic analyses all supported its identity as . Medkleb has a genome size (5825435 bp) which is 1.6 standard deviations smaller than the mean genome size of free-living spp. Medkleb also lacks some genes involved in environmental sensing. Moreover, the Medkleb genome contains at least two recently acquired unique genomic islands as well as genes that encode pectinolytic enzymes capable of degrading plant cell walls. This may be advantageous given that the medfly diet includes unripe fruits containing high proportions of pectin. The results suggest that the medfly harbours a commensal gut bacterium that may have developed a mutualistic association with its host and provide nutritional benefits.
细菌与其昆虫宿主之间的共生关系范围从松散的联系到必需的相互依存。虽然从深入研究专性互利共生中获得了基本的进化见解，但人们对宿主与其肠道微生物组之间灵活共生关系的进化潜力越来越感兴趣。了解微生物和宿主之间的关系也为昆虫控制提供了潜在的利用价值。在这里，我们研究了一种全球性农业害虫——地中海实蝇（）的肠道微生物组。我们使用 16S rRNA 谱分析来比较在不同饮食下饲养的实验室和野生菌株以及从各种自然植物宿主中收集的苍蝇的肠道微生物组。结果表明，实蝇肠道中存在一种简单的微生物组，主要由幼虫饮食决定。然而，无论实验室饮食或自然植物宿主如何， spp. 都主导着实蝇的微生物组，并且对抗生素处理具有抗性。我们对从 Toliman 野生型菌株肠道中分离出的优势假定 spp.（'Medkleb'）进行了基因组测序。全基因组 ANI 分析将 Medkleb 归入 组。使用多基因座系统发育方法解决了 Medkleb 的种级分类学问题 - 分子、序列和表型分析都支持其作为 的身份。Medkleb 的基因组大小为 5825435bp，比自由生活的 spp. 的平均基因组大小小 1.6 个标准差。Medkleb 还缺乏一些参与环境感应的基因。此外，Medkleb 基因组至少包含两个最近获得的独特基因组岛以及编码能够降解植物细胞壁的果胶酶的基因。鉴于实蝇的饮食包括含有高比例果胶的未成熟水果，这可能是有利的。结果表明，实蝇体内存在一种共生肠道细菌，它可能与宿主形成互利共生关系，并提供营养益处。
